Vinyl chloride and vinylidene chloride polymers are known to be self-extinguishing and relatively more flame retardant than other polymers such as polyethylene, polypropylene and the like. However, a substantial amount of smoke may be produced upon exposure of vinyl chloride and vinylidene chloride polymers to a flame. Conventional flame retardants such as antimony oxide do not aid in smoke reduction.
U.S. Pat. No. 3,957,723 discloses a mixture of alumina trihydrate and zinc oxide as smoke retardant in vinyl chloride polymers. U.S. Pat. No. 3,985,706 discloses a mixture of alumina trihydrate and zinc borate as a smoke suppressant for vinyl chloride polymers. U.S. Pat. No. 3,975,359 discloses mixtures of certain nickel compounds and bismuth compounds including Bismuth-subcarbonate as smoke retardants for vinyl chloride and vinylidene chloride polymers.